Roberts Joe. Elementary Number Theory: A Problem Oriented Approach

The MIT Press, 1977. — 672 p. — ISBN10: 0262680289; ISBN13: 978-0262680288.Elementary number theory : a problem oriented approach by Joe Roberts, a professor in the Reed College math department. This book was published by MIT Press in the late 1970s. Visually, it's an amazing book: it is not typeset, but rather is photographically reproduced from a handwritten manuscript. Book is adressed to undergraduates, teachers and for students preparing for international olympiads.